The characters in the novel don't communicate with each other. This leads to misunderstandings and ultimate tragedy. Silence, or at least evasion, is prevalent. This causes the plot twists that occur. Silence about feelings is what ultimately leads to Curley's death, which is a major event. Candy's silence about how he much he loves his dog leads to his having to let it be killed.
Curley's wife's inability to communicate with Curley about her boredom and her lost dreams leads to her being so lonesome that she flirts with other men, causing the tragedy of her death and what it meant to George and Lennie.
The silence of the whole group about what happened to Curley also had significant, but different, impact on all.